I think it was a one shot thing last year. Sort of a yearly special edition. I could be wrong, however. I grabbed one, and inquired MM's Marilyn about it, and she said they may reproduce it, or may go with a new design.
Very cool and dry. Even more so than a standard cob, though the price was a bit steep for a cob.
http://pipesmagazine.com/forums/topic/mm-reverse-calabashes-at-spc
I got one of each color, but was afraid to smoke them. Marilyn scolded me when I stopped by the shop and told her that. So I tried it... and it was great. I still left one un-smoked though.